A pancake axial-air-gap-type synchronous motor is proposed, where the space harmonics power is effectively utilized for the field magnetization instead of the permanent magnets. The pancake axial-air-gap structure, i.e., a single stator with a double rotor configuration, greatly improves the mutual inductance, which is indispensable for the utilization of the space harmonics power for self-excitation. The advantages of the proposed motor are clarified in terms of the torque density with FEM based simulation results.